Nonminimal coupling and quintessence

Recent studies of type Ia supernovas with redshifts up to about z less than or similar to 1 reveal evidence for a cosmic acceleration in the expansion of the Universe. The most straightforward explanation to account for this acceleration is a cosmological constant dominating the recent history of our Universe; however, a more interesting suggestion is to consider an evolving vacuum energy. Several proposals have been put forward along these lines, most of them in the context of general relativity. In this work we analyze the conditions under which the dynamics of a self-interacting Brans-Dicke field can account for this accelerated expansion of the Universe. We show that accelerated expanding solutions can be achieved with a quadratic self-coupling of the Brans-Dicke field and a negative coupling constant omega.